High-capacity radial fit coupling bolts

ABSTRACT

A high capacity radial-fit coupling bolt (or “expanding sleeve bolt”) has a pair of tapered sleeves about a shank of a bolt to which can be applied a tensioning load. An extrudable ring, or a compression ring, is interposed between a head nut or head flange at one end of the shank, and one end of an inner sleeve. A tensioning load is applied to the shank, the inner sleeve causing the outer sleeve to expand diametrically. At a preset load limit, the extrudable ring is extruded through at least one bore in a drive piston between the head nut and the extrudable ring, to allow shank to move relative to the inner sleeve until the tensioning load is fully applied. Alternatively, a drive member is provided between the head nut or head flange and the compression ring, and at a preset limit, the compression ring allows the shank to move relative to inner sleeve until the tensioning load is fully applied. The preset limit will typically correspond to the force required to fully expand the outer sleeve.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

The present application is a U.S. national stage application under 35U.S.C. § 371 of PCT Application No. PCT/AU2013/000209, filed Mar. 6,2013, which claims priority to Australian patent application no.2012900875, filed Mar. 6, 2012, the entireties of which are incorporatedherein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to high-capacity radial fit coupling bolts. (Suchbolts are also known as “expanding sleeve bolts”.)

The invention particularly relates, but is not limited to, high-capacityradial fit coupling bolts used to secure engineering components securelytogether. Examples of potential uses for the bolts include connectingpipeline flanges, drive couplings, machinery mountings and the like.

2. Prior Art

NB: The following discussion is by way of background information only,and is not to be considered a statement of the common general knowledge(CGK) in the area of technology.

When establishing the specifications of drive couplings for powertransmission shafts, engineers calculate the size of the bolts needed byformulae which consider factors such as: (a) coupling diameter, (b)power throughput and (c) materials used to predict bolt size, frequencyand tensile load requirements. Power transmission is ideally made viathe frictional grip between opposing coupling faces, but will usuallyalso consider the resistance to shear forces which may be directedagainst the bolts' shanks during operation. Where the shear forces mayoccur as a result of vibration, slippage and/or lack of bolt tension,the impingement of coupling bolt holes against their respective boltshanks often damages and distorts these components, making disassemblyextremely difficult. It can be seen that the application and maintenanceof the specified bolt tension in all the bolts is vital in maintainingthe efficacy of the drive couplings. It can also be seen that a boltwhich can expand radially to fill any void formed by the tolerancebetween bolt shank and its respective bolt holes in the drive couplingwill substantially assist limiting any slippage of the coupling faces.

For some years it has been common practice to employ bolts which havethis capacity. In currently used types, which are commonly referred toas “Radial Fit Coupling Bolts”, the bolt component is manufacturedhaving an enlarged, tapered portion at the midsection of the shank withscrew-threaded portions at each end. The tapered section of the bolt isreceived within a complementary-shaped tapered sleeve which, when placedin position through aligned bolt holes in the drive coupling componentsto be clamped, is diametrically expanded by the action of drawing thetapered portion of the shank into the tapered sleeve. This diametricalexpansion will continue in response to the applied force until thesleeve completely fills the bolt holes through the coupling components.

Typically in such a bolt, the external tapered surface of the centralportion of the shank and the inner surface of the sleeve must bemanufactured to a very fine finish, and may require the surfaces to bepolished. In addition, a ‘track” may be machined in the tapered surfaceof the central portion of the shank. The inner taper may become lockedinside the external sleeve and difficult to remove, requiring theinjection of oil under pressure to eject the bolt and to allow thesleeve to collapse; and as the sleeve is diametrically expanded, theportions overlying the “track” do not expand to the same extent. Whenthe components secured by the bolt are to be released, the sleeve mayjam about the central portion of the shank and remain in relatively highfrictional engagement with the aligned bolt holes in the components,requiring considerable force e.g. applied by a press, to release thebolt from the bolt holes.

The manufacturers of these known bolts recommend that a back nut befitted to the screw-threaded portion at one end of the bolt shank (toengage one of the coupling components); a tensioning load applied to theother end of the bolt shank; and, when the desired expansion of thesleeve is achieved, the tensioned other end of the shank may then belocked in place by tightening down a nut on that end, the nut engagingthe second of the coupling components.

Such designs exhibit a clear disadvantage in that the original “setting”of the sleeve will lock the bolt in place via sticking friction. Thus,when the bolt is tensioned with the back nut in place, very little ofthe applied tensile load will migrate past the tapered section of theshank to tension the opposite end thereof and lock the back nut. Thismay be redressed by tightening the shank from that end also, but willhave the effect of decreasing the “setting” force which occasions thediametrical expansion of the sleeve.

OBJECT OF THE INVENTION

It is an object of the present invention to provide a design for ahigh-capacity radial fit coupling bolt, or high-capacity expandingsleeve bolt, which overcomes, or at least ameliorates, the problems ofthe prior art.

Other preferred objects of the present invention will become apparentfrom the following description.

SUMMARY OF THE INVENTION

In one aspect, the present invention resides in a high-capacity radialfit coupling bolt assembly, or high-capacity expanding sleeve boltassembly, to secure at least two components together, the assemblyincluding:

a shank having a substantially cylindrical central portion intermediatefirst and second end portions;

respective inner and outer sleeves surrounding at least a section of thecentral portion of the shank, the inner and outer sleeves havingcomplimentary respective outer and inner tapered engagement faces; and

an extrusion ring interposed between a first end of the inner sleeve anda drive piston at or adjacent the first end portion of the shank, thedrive piston having at least one axial bore open to the extrusion ring;

so arranged that, as a tensioning load is increasingly applied to thesecond end portion of the shank, relative axial movement between theinner and outer sleeves will cause the outer sleeve to expanddiametrically into engagement with the at least two components up to apreset limit, at which the extrusion ring will at least be partiallyextruded through the at least one axial bore, thereby allowing the shankto move relative to the inner and outer sleeves and at least twocomponents.

In a second aspect, the present invention resides in a high-capacityradial fit coupling bolt assembly, or high-capacity expanding sleevebolt assembly, to secure at least two components together, the assemblyincluding:

a shank having a substantially cylindrical central portion intermediatefirst and second end portions;

respective inner and outer sleeves surrounding at least a section of thecentral portion of the shank, the inner and outer sleeves havingcomplimentary respective outer and inner tapered engagement faces; and acompression ring interposed between a first end of the inner sleeve anda drive member at or adjacent the first end portion of the shank;

so arranged that, as a tensioning load is increasingly applied to thesecond end portion of the shank, relative axial movement between theinner and outer sleeves will cause the outer sleeve to expanddiametrically into engagement with the at least two components up to apreset limit, at which the compression ring will allow the shank to moverelative to the inner and outer sleeves and to the at least twocomponents.

Preferably, as the tensioning load is initially applied to the secondend of the shank, the compression ring will axially move the innersleeve relative to the outer sleeve to expand the outer sleevediametrically, while allowing the shank to move relative to the innersleeve and thereby allow the tensioning load to be applied along thefull length of the shank.

Preferably, the first end portion is formed with an integral headflange; or is screw-threaded to receive a head nut; the head flange orhead nut being engageable with an abutment face on an end of one of thecomponents.

Preferably, the head flange or head nut has an annular ring portionwhich extends into a first annular cavity, defined by a bolt hole in theone component and the first end portion of the shank, to engage an outerannular face of the head member, the inner face of the head memberengaging the first end of the inner sleeve.

Preferably, the second end portion of the shank is screw-threaded, orotherwise profiled, to be releasably engaged by a tensioning apparatus,where the tensioning apparatus, or a tensioning nut on the second endportion, is engageable with an outer annular end face of the outersleeve.

Preferably, the outer sleeve has a peripheral flange, forming theannular outer face, with an annular inner face engaging the second ofthe components.

Preferably, the inner sleeve has a body with a cylindrical bore forslidable movement on the central portion of the shank. Preferably, aperipheral flange at a first end of the body is slidably received withina bolt hole in the first of the components and provides an annularabutment face at the one end engaged by the extrusion ring.

Preferably, the outer tapered engagement face of the inner sleeve, andthe inner tapered engagement face of the outer sleeve, is inclined at arelatively shallow angle to the longitudinal axis of the bolt assembly.Preferably, the angle of inclination is less than 10°; more preferablyless than 7.5°; most preferably in the range of 0.5°-5°.

Preferably, the inner and outer sleeves will be manufactured from metalsor alloys, with at least the outer sleeve having a relatively thin wallthickness, to enable the outer sleeve to expand diametricallysufficiently to fill the working clearance between the outer sleeve andthe set of aligned bolt holes (in the at least two components), enablingthe bolt assembly to be inserted therein before tensioning. Typicallythe working clearance will not exceed 0.5 mm, more preferably 0.3 mm.

Preferably, grease, graphite, or other suitable lubricant, is applied toat least one of the tapered engagement faces before the bolt assembly isassembled, to assist the relative axial movement between the inner andouter sleeves as the bolt assembly is both tensioned and released.

Preferably, the shank, the drive piston, and the head and tail nuts willbe manufactured from high-tensile steel.

Preferably, the outer sleeve has a body with a cylindrical outer faceslidably received in a bolt hole of a second of the components.

Preferably, the drive piston has a plurality of equally-spaced axialbores therethrough.

Preferably, the extrusion ring is manufactured from a “flowable”material. Suitable materials includes rubbers (natural and/orsynthetic); polymers, including Nylon (Trade Mark), polyethylene,polypropylene or the like; “soft” metals, such as lead, tin or aluminiumor alloys thereof; “harder” metals, such as bronze; or other suitable“flowable” material(s).

In a third aspect, the present invention resides in a method of securingat least two components together, the components having at least one setof aligned bolt-holes, including the steps of:

(a) inserting a high-capacity radial fit coupling bolt assembly, havingthe extrudable ring, into one set of the aligned bolt holes, with thehead flange or head nut having an inner face optionally spaced a smalldistance from an end face of a first of the components (and, optionally,an annular end portion on the head flange or head nut received in thebolt hole of the first component);

(b) applying a tensioning load to the second end portion of the shank toaxially draw the inner sleeve into the outer sleeve; wherein:

(c) the engagement between the outer tapered engagement face on theinner sleeve with the inner tapered engagement face of the outer sleevescauses the cylindrical outer face of the outer sleeve to expanddiametrically into engagement with the one set of bolt holes in thecomponents; and

(d) as the tensioning load further is increased above a preset limit,the extrusion ring will at least be partially-extruded through the atleast one axial bore in the drive piston to allow the shank to moverelative to the inner sleeve (and thereby the components) until the headflange or head nut is engaged with the first of the components and thedesired tensioning load has been applied to the shank to secure the atleast two components together.

In a fourth aspect, the present invention resides in a method ofsecuring at least two components together, the components having atleast one set of aligned bolt-holes, including the steps of:

(a) inserting a high-capacity radial fit coupling bolt assembly, havingthe compression ring, into one set of the aligned bolt holes, with thehead flange or head nut having an inner face optionally spaced a smalldistance from an end face of a first of the components (and, optionally,an annular end portion on the head flange or head nut received in thebolt hole of the first component);

(b) applying a tensioning load to the second end portion of the shank toaxially draw the inner sleeve into the outer sleeve; wherein:

(c) the engagement between the outer tapered engagement face on theinner sleeve with the inner tapered engagement face of the outer sleevescauses the cylindrical outer face of the outer sleeve to expanddiametrically into engagement with the one set of bolt holes in thecomponents; and

(d) as the tensioning load is further increased above a preset limit,the compression ring will allow the shank to move relative to the innerand outer sleeves and to the at least components.

Preferably, during step (b), the compression ring will move the innersleeve relative to the outer sleeve to expand the outer sleevediametrically, while allowing the shank to move relative to the innersleeve and thereby allow the tensioning load to be applied along thefull length of the shank to secure the at least two components together.

Preferably, after step (d), in a further step (e), a tensioning nut isengaged with screw-threads on the second end portion of the shank and isrotatably moved there-along into tensioned engagement with a second ofthe components, before release of the tensioning apparatus from thesecond end portion of the shank. (In this embodiment, the tensioning nutis received on the second end portion of the shank inwardly of theconnection between the second end portion of the shank and thetensioning apparatus.)

Alternatively, after step (d), in a further step (e), a hydraulic nut,which operates as the tensioning apparatus, and which engages the secondof the components, is operated normally, by engaging its locking deviceand releasing the charge pressure.

BRIEF DESCRIPTION OF THE DRAWINGS

To enable the invention to be fully understood, and to enable theskilled addressee to put the invention into practice, a number ofpreferred embodiments will now be described, with reference to theaccompanying illustrations, in which:

FIG. 1 is an isometric view of a coupling assembly between the flangesof two drive shafts employing a plurality of hydraulic nuts fitted torespective coupling bolts of a first embodiment of the presentinvention;

FIG. 2 is a part-sectional isometric view of the coupling assembly;

FIG. 3 is a sectional side elevation view of the coupling assembly, withthe coupling bolt of the first embodiment prior to the application ofthe tensioning load to the bolt shank; and

FIG. 4 is a sectional side elevational view of a coupling assemblybetween two machine components, with a coupling bolt of the secondembodiment prior to the application of the tensional load to the boltshank.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The skilled addressee will appreciate that the embodiments of thepresent invention to be hereinafter described are designed forapplications where the shear loads on the bolt shanks may be extreme.The coupling bolts of the present invention may be used in drivecouplings or other devices for transmitting extremely high rotationalloads; but are also suitable for installations such as the mountingbolts for large machines (such as marine liquid- or gas-fuelledengines), pillars or beams for buildings, or the like.

Referring to FIGS. 1 to 3, a drive coupling assembly 100 interconnectsthe respective flanges 7 of a pair of respective drive shafts 101, 102.

As will be hereinafter described in more detail, the coupling assembly100 incorporates a plurality of coupling bolts 10, in accordance with afirst preferred embodiment of the present invention, provided at equalangular spacing's around the flanges 7, where the coupling bolts 10 aretensioned by respective hydraulic nuts 8.

FIG. 3 illustrates a first embodiment of the present invention, whereeach high-capacity radial fit coupling bolt (or expanded sleeve bolt)10, is provided with a hydraulic nut 8, e.g., of the type manufacturedand sold by Technofast Industries Pty Ltd, 2/677 Boundary Road,Richlands, Queensland, Australia, under the Registered Trade Mark“TECHNOFAST”.

The coupling bolt 10 has a shank 1 with a cylindrical central portion 11intermediate screw-threaded first and second end portions 12, 13.

A head nut 5 is screw-threadably engaged with the first end portion 12of the shank 1 and has an annular end portion 51 on its inner face. Theskilled addressee will note that the annular end portion 51 on the headnut 5 is received within a cavity defined by the bolt hole 71 of thefirst of the components 7 and the shank 1.

An inner sleeve 3 has a tubular body 31 with a cylindrical bore 32 forslidable movement on the central portion 11 of the shank 1. At the endof the body 31 adjacent the first end portion 12 of the shank 1, aperipheral flange 33 is slidably received in the bolt hole 71 in thefirst component 7 and has an annular abutment face 34 at its outer end.

The body 31 of the inner sleeve 3 has an outer tapered engagement face35 where the angle of inclination of that face to the longitudinal axisof the shank 1 is in the range of 3°-5°.

The outer sleeve 2 has a tubular body 21 with a cylindrical outer face22 which has a working clearance of 0.3 mm-0.5 mm with the boltholes 71,72 of the first and second components before the bolt assembly 10 istensioned. At the end of the body 21 adjacent the second end portion 13of the shank 1, a peripheral flange 23 has an inner annular abutmentface 24 is engageable with an adjacent face of the second component 7,and an outer abutment face 25 on the body 21 of the outer sleeve 2 isengageable by an outer portion 81 of the hydraulic nut 8, the innerportion 82 of the hydraulic nut 8 being screw-threadably engaged withthe second end portion 13 of the shank 1.

The body 21 of the outer sleeve 2 has an inner tapered engagement face26 inclined at the same angle to the shank 1 as the outer taperedengagement face 35 of the inner sleeve 3.

A driving piston 6 has an annular body 61 with a plurality ofequally-spaced axial bores 62 extending therethrough. The annular body61 is screw-threadably mounted on the first end portion 12 of the shankadjacent the end of the central portion 11.

An extrusion ring 4, having a tubular body 41, is interposed between theannular abutment face 34 on the inner sleeve 3 and inner annularabutment face 63 of the driving piston 6. The inner bore of the body 41is slidably engaged with the central portion 12 of the shank 1; and theouter face is aligned with the outer face 22 of the outer sleeve 2.

The bolt assembly 10 is assembled and inserted in the aligned bolt holes71, 72 as shown in FIG. 3.

The skilled addressee will note that the inner face of the head nut 5 isspaced from the adjacent face of the first component 7 and that theperipheral flange 33 on the inner sleeve 3 is spaced from the adjacent(inner) end of the body 21 of the outer sleeve.

As the hydraulic nut 8 is charged, the inner portion 82 of the hydraulicnut 8 will move in the direction of arrow A, causing the annular endportion 51 on the head nut 5 to engage the driving piston 6 and urge thedriving piston 6, extrusion ring 4 and inner sleeve 3 towards the outersleeve 2. The sliding engagement between the respective outer taperedengagement face 34 of the inner sleeve 2 with the inner taperedengagement face 26 of the outer sleeve 2, thereby diametricallyexpanding the outer sleeve 2 into engagement with the aligned bolt holes71, 72 in the components 7.

When the desired tensioning load has been applied to the shank 1 by thehydraulic nut 8, the hydraulic nut 8 may be isolated from the source ofthe hydraulic fluid under pressure to lock the hydraulic nut 8 undertensile load.

At a preset tensioning load, the “flowable” material of the body 41 ofthe extrusion ring 4 will commence to flow through the axial bores 62 inthe body 61 of the driving piston 6. This will limit any furtherrelative movement between the inner and outer sleeves 3, 2; but willallow the driving piston 6, and head nut 5, to continue to move in thedirection of arrow A until the inner face of the head nut 5 engages theadjacent face of the first component 1 and the desired tensioning loadis applied along the length of the shank 1.

If the coupling components 7 are to be separated, e.g., for maintenance,the hydraulic pressure in the hydraulic nut 8 is released, allowing theshank 1 to be moved in a direction opposite to arrow A to relieve thetensioning load on the bolt assembly 10. The inner sleeve 3 will tend tomove in the direction opposite to arrow A, reducing thediametrically-applied forces on the outer sleeve 2. The head nut 5 isreleased from the first end portion 12, of the shank 1, enabling thefirst end portion 12 of the shank 1 to be pressed in the direction ofarrow A, to release the bolt assembly 10 from the components 7.

In a second embodiment, not illustrated, a tensioning (or tail) nut maybe interposed between the tensioning apparatus (connected to the secondend portion 13 of the shank 1) and the outer sleeve 2. In thisembodiment, the tensioning apparatus applies a tensioning load to theshank 1 to cause the inner sleeve 3 to be axially moved along thecentral portion 11 of the shank 1 to diametrically expand the outersleeve 2 as hereinbefore described.

When the desired tensioning load has been applied, the tensioning (ortail) nut is rotated to move along the second end portion 13 in adirection opposite to the direction of arrow A, until it engages theouter abutment face 26 of the outer sleeve 2 to maintain the tensioningload on the shank 1. The tensioning apparatus, e.g., a hydraulic jack,can then be removed.

In this embodiment, to enable the components 7 to be separated, thetensioning apparatus is reconnected to the second end portion 13 of theshank 1 and a tensioning load is applied to the shank 1 to enable thetensioning (or tail) nut to be rotatably released from its engagementwith the outer sleeve 2; and the tensioning apparatus is released fromthe second end portion 13 of the shank 1. The head nut 5 is releasedfrom the first end portion 12 to enable the bolt assembly 10 to bewithdrawn as hereinbefore described.

It will be readily apparent to the skilled addressee that the couplingbolt 10 as hereinbefore described can provide considerable clampingforces between the opposed faces of the components 7 which are infrictional engagement, and can withstand and oppose even extreme shearforces opposing the relative rotation of the components 7.

The selection of the materials and/or dimensions for the extrusion ring6, the outer sleeve 2 and the inner sleeve 3 will depend on the intendedapplications for the bolt assembly 10. Preferably, the outer sleeve 2will have a relatively thin wall, of metal or metal alloy, to enable thediametrical expansion of the outer sleeve 2 when the inner sleeve 3 isforced therein as the shank 1 is tensioned.

The materials for the manufacture of the extrusion ring 4 may beselected from a wide range of polymer/plastics material; or metal/metalalloys; or the like. As hereinbefore described, the materials may rangefrom Nylon, through lead, aluminium, to bronze, depending on the presetlimit of the tensioning load at which the body 41 of the extrusion ring4 commences “flowing” through the axial bores 62 in the body 61 of thedriving piston 6, to thereby allow the shank 1 to continue to moverelative to the components 7 until the desired tensioning load isapplied to the shank 1, that load being evenly distributed along theshank 1.

FIG. 4 illustrates a coupling assembly, of a second embodiment, betweena pair of machine components 107 (with an interposed spacer S andgaskets or seals G) employing a coupling bolt 110 of the secondembodiment of the present invention.

The shank 101, inner and outer sleeves 102, 103 and the head nut 105 aresubstantially as hereinbefore described, with reference numerals 1xxcorresponding to reference numerals xx for the same items in FIGS. 1 to3.

The drive piston 6 of the first embodiment is replaced by a drive member106, in the form of a lock-nut screw-threadably engaged on the shank101, with the outer face 161 of the drive member 106 spaced from theannular end portion 151 of the head nut 105.

The extrusion ring 4 of the first embodiment is replaced by acompression ring 104, of substantially frusto-conical shape e.g. in theform of a Belleville washer.

The divergent inner face 141 of the compression ring 104 engages theabutment face on the end of the inner sleeve 103, while the peripheralouter face 142 of the compression ring 104 engages the inner face 162 ofthe drive member 106.

As the hydraulic tensioner 108 applies a tensioning load, the divergentface 141 of the compression ring 104 engages the inner sleeve 103 toaxially move the inner sleeve 103 relative to the outer sleeve 102 tocause the outer sleeve 102 to expand diametrically, while allowing theshank 101 to move within the inner sleeve 103 and for the shank 101 tobe tensioned along its full length. The shank 101 can also pull the headnut 105 into engagement with the adjacent component 107. This enablesthe tensioning load to be evenly applied along the length of the shank101. The divergent face 141 of the compression ring 104 may cause theinner sleeve 103 to expand diametrically into engagement with the outersleeve 102.a

When the tensioning load reaches a preset limit, when the outer andinner sleeves 102, 103 are fully engaged, the compression ring 104 willallow the shank 101 to move relative to the outer and inner sleeves 102,103, and thereby relative to the two components 107, to ensure that thebolt 110 is evenly tensioned along its full length.

The tensioning load on the shank 101 can be maintained by the chargedhydraulic jack 108; the lock nut may be engaged and the hydraulic jack108 removed; and the components separated 107; in the same manner; asfor the first embodiment of FIGS. 1 to 3.

Unlike the extrusion ring 4, the compression ring 104 may be reused,provided its mechanical limits have not been exceeded.

While only a single Belleville washer has been illustrated as thecompression ring 104, two or more such Belleville washers (or the like)may be provided to provide greater axial movement of the bolt shanks 1,101 relative to the “locked up” sleeves 2, 3 and 102, 103.

In both embodiments, the “preset limit” will correspond to the forcerequired to expand the outer sleeve 2, 102 into engagement with thecomponents 7, 107; but other such limits e.g. distance of axial movementof the shank relative to the components, or to the outer sleeve.

The skilled addressee will appreciate that the present inventionprovides coupling bolts with advantages which include, but are notlimited to:

a) The coupling bolts are simpler to manufacture and/or operate, and aremore cost effective;

b) The coupling bolts provide bolts of a “one pull” bolt design whichenables the sleeve setting and bolt tensioning in a single action; and

c) The bolts can be more easily removed when the tension is released.

Various changes and modifications may be made to the embodimentsdescribed and illustrated without departing from the present invention.

The invention claimed is:
 1. A high-capacity radial fit coupling boltassembly, or high-capacity expanding sleeve bolt assembly, to secure atleast two components together, the assembly including: a shank having asubstantially cylindrical central portion intermediate first and secondend portions; respective inner and outer sleeves surrounding at least asection of the central portion of the shank, the inner and outer sleeveshaving complimentary respective outer and inner tapered engagementfaces; and an extrusion ring interposed between a first end of the innersleeve and a drive piston at or adjacent the first end portion of theshank, the drive piston having at least one axial bore open to theextrusion ring; so arranged that, as a tensioning load is increasinglyapplied to the second end portion of the shank, relative axial movementbetween the inner and outer sleeves will cause the outer sleeve toexpand diametrically into engagement with the at least two components upto a preset limit, at which the extrusion ring will at least bepartially extruded through the at least one axial bore, thereby allowingthe shank to move without displacing the outer sleeve relative to the atleast two components.
 2. The assembly of claim 1, wherein: the first endportion is formed with an integral head flange; or is screw-threaded toreceive a head nut; the head flange or head nut being engageable with anabutment face on an end of one of the components.
 3. The assembly ofclaim 2, wherein: the head flange or head nut has an annular ringportion which extends into a first annular cavity, defined by a bolthole in the one component and the first end portion of the shank, toengage an outer annular face of the head member, the inner face of thehead member engaging the first end of the inner sleeve.
 4. The assemblyof claim 1, wherein: the second end portion of the shank isscrew-threaded, or otherwise profiled, to be releasably engaged by atensioning apparatus, where the tensioning apparatus, or a tensioningnut on the second end portion, is engageable with an outer annular endface of the outer sleeve.
 5. The assembly of claim 1, wherein: the outersleeve has a peripheral flange, forming the annular outer face, with anannular inner face engaging the second of the components.
 6. Theassembly of claim 1, wherein: the inner sleeve has a body with acylindrical bore for slidable movement on the central portion of theshank; and optionally, a peripheral flange at a first end of the body isslidably received within a bolt hole in the first of the components andprovides an annular abutment face at the one end engaged by theextrusion ring.
 7. The assembly of claim 1, wherein: the outer taperedengagement face of the inner sleeve, and the inner tapered engagementface of the outer sleeve, is inclined at an angle to the longitudinalaxis of the bolt assembly; where the angle of inclination is optionallyless than 10°; more optionally less than 7.5°; most optionally in therange of 0.5°-5°.
 8. The assembly of claim 1, wherein: the inner andouter sleeves will be manufactured from metals or alloys with at leastthe outer sleeve having a wall thickness to enable the outer sleeve toexpand diametrically sufficiently to fill the working clearance betweenthe outer sleeve and the set of aligned bolt holes in the at least twocomponents, enabling the bolt assembly to be inserted therein beforetensioning, optionally with a working clearance not exceeding 0.5 mm,more optionally 0.3 mm.
 9. The assembly of claim 1, wherein: grease,graphite, or other suitable lubricant, is applied to at least one of thetapered engagement faces before the bolt assembly is assembled, toassist the relative axial movement between the inner and outer sleevesas the bolt assembly is both tensioned and released.
 10. The assembly ofclaim 1, wherein: the shank, the drive piston, and the head and tailnuts will be manufactured from high-tensile steel.
 11. The assembly ofclaim 1, wherein: the outer sleeve has a body with a cylindrical outerface to be slidably received in a bolt hole of a second of thecomponents.
 12. The assembly of claim 1, wherein: the drive piston has aplurality of equally-spaced axial bores therethrough.
 13. The assemblyof claim 1, wherein: the extrusion ring is manufactured from rubbers(natural and/or synthetic), polymers comprising polyethylene orpolypropylene, lead, tin, aluminium or alloys thereof or bronze.
 14. Amethod of securing at least two components together, the componentshaving at least one set of aligned bolt-holes, including the steps of:(a) inserting a high-capacity radial fit coupling bolt assembly, asclaimed in claim 1, into one set of the aligned bolt holes, with thehead flange or head nut having an inner face optionally spaced a smalldistance from an end face of a first of the components (and, optionally,an annular end portion on the head flange or head nut received in thebolt hole of the first component); (b) applying a tensioning load to thesecond end portion of the shank to axially draw the inner sleeve intothe outer sleeve; wherein: (c) the engagement between the outer taperedengagement face on the inner sleeve with the inner tapered engagementface of the outer sleeves causes the cylindrical outer face of the outersleeve to expand diametrically into engagement with the one set of boltholes in the components; and (d) as the tensioning load further isincreased above a preset limit, the extrusion ring will at least bepartially-extruded through the at least one axial bore in the drivepiston to allow the shank to move relative to the inner sleeve (andthereby the components) until the head flange or head nut is engagedwith the first of the components and the desired tensioning load hasbeen applied to the shank to secure the at least two componentstogether.
 15. The method as claimed in claim 14, wherein: after step(d), in a further step (e), a tensioning nut is engaged withscrew-threads on the second end portion of the shank and is rotatablymoved there-along into tensioned engagement with a second of thecomponents, before release of the tensioning apparatus from the secondend portion of the shank, the tensioning nut being received on thesecond end portion of the shank inwardly of the connection between thesecond end portion of the shank and the tensioning apparatus.
 16. Themethod as claimed in claim 14, wherein: after step (d), in a furtherstep (e), a hydraulic nut, which operates as the tensioning apparatus,and which engages the second of the components, is isolated from asource of hydraulic fluid when the desired expansion of the outer sleeveand/or tensioning load within the shank is achieved.